Telephone trunking system.



F. M. DAVIS.

v TELEPHONE TRUNKING SYSTEM.

APPLIOATION FILED SBPT.14, 190s.

'1 0'26,85Q Patented May 21, 1912.

WdpeJ/e/ 'Frecl-M paw [QUE for UNITED STATES PATENT- oFFroE.

FRED M. DAVIS, OF CHICAGO, ILLINOIS, ASSIGNOR T KELLOGG' SWITCHBOARD AND SUPPLY COMPA I IYyOF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

' TELEPHONE TRUN'KING SYSTEM.

I r Specification of Letters Iatent.

T 0 all whom it may concern:

Be it known that I, FRED M. DAVIS, a citizen of the United States, residing in Chicago, county of Cook, and State-of Illinois,

haveinventedcertain new and useful .Iin} provements 1n Telephone Trunking Sys-[ tems, of which the following is a specification.

My invention relates to telephone trunking systems of the character adapted to be or fit usedin both directions such that the.

supervisionwould be different when used: in one direction from that when the trunkwas used in the'other direction. Iv

It is the object of my invention to pro vide a trunk circuit which' shall ternilnate in multiple jacks at eachend 'and'lwhich shall be provided with a lamp signal at each end, the two signals being adaptedto indicate when a connection has been established at the other end-of the trunk.

My invention is illustrated in the accompanying drawing in which all apparatus is shown in its normal or unactuated condition and in which two connecting circuits are shown in position" to'he united by a trunk circuit. The upper and lower connecting circuits and the telephone llDQSdllllSt-rilttd in connection therewith are duplicates and the apparatus of said circuits will be desig' natedby like figures, the figures-for the lower circuit being provided with the sutfix'. H I

Substation 1 is equipped with the usual condenser 2 and annunciat-or 3 connected in a permanent bridge betwee'n line conductors 4 and 5 and with the transmitter 6 and receiver 7 in a bridge maintained normally open by contacts of the switch hook 8. At the central office, line conductor 5 is connected through contacts 9 and 10 of cut-oil relay 11 and the coil of line relay 12, and conductor 13 with thelive pole of battery 14. and line conductor 4 connects with earth through contacts 15 and 16 of cut-oft relay ll. Line relay 12 controls the normally open contacts 17 and 18 in the circuit of-t he line lamp 19. .Cut-ofi' relay 11 also has the normally open inside contacts 20 and 2l, the

Patented May 21, 1912.

- Application filed September 14, 1908. Serial No. 452,827.

of relay 11 with earth, and also with the sleeve contacts 22 of the multiple jacks. The contact 20 is connected withthe tip contacts 23 of the multiple \jacks. The cord circuit to connect with this line is of the well known two'conductor type, the tip strand conductors 2S and 29, contacts of the ringing key to the tip 31 of the calling plug. The sleeve strand extends from the sleeve to the sleeve contact 36 of the calling plug.

calling relays 38 and 39 being connected in ends of thetip conductor,'and the ground live pole of battery 14. The answering relays- 38 and 40 eontrolthe'local circuit of the answering supervisory signal 42, and the calling supervisory relays 39 and 41 control the local circuit of the calling supervisory signal 43.

The sleeve calling supervisory relay 41 has additional contacts 44, 45 and 46, conmaintaining a separation between the pot"- tions 28 and 29 of the tip talking strand of the cord circuit. Contacts 45 and 46 are normally closed, contact -l6 being connected through conductor 47 and the normally open auxiliary contacts 48 and 49 of the operators listening key 50 through the impedance coil 51 to earth and through the condenser 52 and the tertiary winding of the operators induction coil 53 with the live pole of battery 14.

The operation of the operators listening key 50 is adapted to place the operators head receiver 54 and condenser 55 in a bridge between the talking strands of the cord circuit. The operators ringing key 30 is adapted when actuated to connect the ringing generator 57 with the tip of the calling plug and is adapted to connect the sleeve of the calling plug with the live pole contact 21 beil-igconne cted through the coil extending ffrom the tip 25 of't-he answering plug through conductor 26, condenser 27,

contact'32 of 'the answering plug through conductor 33, condenser 34, conductor 35, a and sleeve contacts of the ringing key 30 1o This cord circuit is provided with four, supervisory relays, the tip answering and.-v

a bridge between the answering and calling tacts 44 and 45 being normally open and pole of battery 14, and the answering and -,calling sleeve supervisory relays 40 and 41 being connected between the answering. and calling ends of the sleeve conductor and the of battery 14 through the non-inductive re- I connected withthe inside contact 61 of cutoff relay 62 and also through the coil of that relay with. earth.- The tip contacts 63 normally open contacts 68and 69in the cir- '-.cuit f the trunk line lamp 70.J'Spring conof the jacks are connected, with the other normally open inside contact 64 of cut-0H relay 62. The spring 65 of said cut-off relay is adapted when actuated to connect with the contact 64, but in its normal .con-

dition connects through contacts 66 and the coil of the line relay 67 with the live pole of battery 14, this line relay 67 controlling tact7l of cut-off relay 62 is adapted when actuated to connect with th'ejnormally open inside contact 61, but normally connects through contact 72 with earth.

' The springs 65 and 71 of cut-oflirelay 62 flare connected respectively with the trunk me connecting at the other exchange through condenser 75 with the-tip contacts 76 of the multiple jacks and conductor 74 connecting through condenser 77 with the sleeve contacts 1 7-8 of the multiple jacks. The trunk conductor 73 also connectsthrough condenser '79, the operating coil'of relay 80 and contacts'Sl and 82 of relay 83 with the trunk conductor 74'. Line conductor 73 also is connected through the conductor 84 with the open multiple contacts 85 of the multiple jacks, the other open contact ,86 being connected through conductor 87, coil of polarized relay 88 and the coil of relay 83 withf'the other trunk conductor 74. Relay 86 has a lockingwinding by which its con- .tacits :-89. and 90 are adapted to be maintain'ed 'closed, these contacts being adapted to complete the circuit of the trunk signal 91. C ontact'89 of relay 80 is connected with earth through contacts 92 and 93 of relay 83. The impedance coil v94 has two windings, one of which is bridged between the'multiple contacts 7 6' and 78 of the'jacks, this bridge containing the contacts 95 and 96 of the polarized relay 88, and the other of which is connected between the sleeves of the jack and earth.

In the operation otmy systeni' a call will first be traced as arlsing at substation 1.

The subscriber at that station removes his receiver7 from the switch hook 8 and thereby completes a circuit from the live pole of battery 14 through conductor 13, line relay 12, contacts 10 and 9- of cutofirelay 11, line conductor 5, transmitter6, receiver 7, switch hook 8, line conductor 4, and'con tacts 15 and-16 of cut-ofl relay 11 to ground. The current in this path actuates line relay connects the contacts of conductors 73 and-74, conductor 731 12 closing its contacts 17 and 18 and completing the circuit of the line lamp 19, which lamp is displayed to indicate to the operator that a connection is desired. The operator seeing the display of this.signal,inserts her answering plug into the answering jack thus designated, and thereby completes circuit from the live pole, of battery 14;, through the coil. of supervisory rela --40,."

conductor 33, contacts 32 and 22 ot the plug and jack and the coil of cut-.ofl'. relay- 11 toground. The current in this path actuates relays 40 and 11. The actuation of relay 11 interrupts the 'circug't of the'line relay 12 and efiaces the line lamp, and also the jack directly with the lamps of the telephone line. Upon the actuation of relay 11 therefore, a fur ther circuit is completed from thelive pole of battery 14- throughrthec coil of supervisory relay 40, conductor'33, contacts '32- and 22 of the plug and ack, contacts 21 and 9 of cut-ofl relay11,',line conductor 5,-trans mitter 6, receiver 7 ,sWitch hook 8,line conductor 4, contacts15 and 20 of cut-oitrelay 11, contacts 23 and 25 of the jack'and plug, conductor 26 and the coil of supervisory relay 38 to the ground pole'of battery 14. w The current in this latter path not only main- I 'tains the actuation ofrelay 40 but also actuates relay 38,, thus leaving the circuit of the supervisory slgnal 42 in an un-energized condition. The operator now inquires the desired number and finding it to be that of a subscriber at the other exchange, inserts key ground. The .'currentin' this path actuates the relays 62 and 41. The actuation of relay 41v closes the'circuit of the supervisory signal 43 and displays'that signal and also closes the normal interruption between the 44. The actuation of cut-ofi' relay 62 con nects the limbs- .7 3 and 74.respectively with .the tip and sleeve contacts of the jack. The

operator now throws her ringing key and generator 57 through the tip contacts 31 and 63 of the plug and jack, contacts 64 and 65 I of cut-ofi' relay 62, line conductor 73, condenser .79, the operating coil of relay 80,

ductor 74, contacts 71 and 61 of cut-off re-- lay 62, sleeve'contacts 60 and 36 of the jack and plug and the non-inductive resistance 58 through the battery 14 baclr tothe 30, sleeve contacts 36 and 60 of the plug 7 i and jack, andthe coilofcut-oif relay 62 to her calling plug into the jack ofthe trunk line extending to the other exchange, the operator conductors 28 and 29 atits' contacts 45 and 12 0 sends alternating ringing current from the 3 contacts'81 and 82 of relay 83, trunk 0011- ground pole of the generator 57; The current in this path 'actuates the relay 80 which -"closes alocking circuit for itself, this cir- 1 tactstiti and 60 of the plug and 'jack, contacts'fil'and 71 of cut-otl' relay (32, line concuit including the locking coil of relay 80 in -one branch and the trunk signal 90 in another branch. l e

The operator at the second exchange seeing the signal 91 displayed, inserts her an- @swering plug into the jack designated by the display of the signal 91. In so doing'the auxiliary contacts 85 and 8(5 of the trunk jack are closed and a circuit is completed from the live pole of battery 14- through the coil of supervisory relay 41, conductor 35, sleeve contacts of ringing key 30, sleeve con 3 ductor 't t, the coils of relay S3 and 88, conat the other end of the trunk has established.

her connection withthe trunk. Current 11! the path before describedalso actuates relay 83 which interrupts the circuit of the operating coil of relay 80 so that that coil is no longer bridged across-;lthe talking circuit. The actuation of relay 83' also severs the locking circuit of relay Stlallowing that re lay to fall back and efi'ace the trunksignal 91. The current which now passes through the coil of the polarized relay 88 is inthe proper direction to maintain thecontacts 95 battery 14 through the coil of supervisoryrelay40i', conductor 33, contacts and 9G offthat relay in their closed condition, and therefore, upon the insertion of the answering plug of the second circuit, a circuit is completed from thelive pole of of the plug and jack, the winding of impedance coil 94, contacts 96 and 95 of polarized relay 88, the tip contacts 76 and 27 of the jack audplug, conductor 26" and the coil of dition.

cut-ofi 'relay 38 to the ground pole of'battery 14. Current in this path actuates both relays 40' and 38. leaving the circuit of supervisory signal 42 in its dei nergizcd con- The operator now obtains the desired number either from the calling s bscriber or from the first operator and inserts her calling plug into the jack of the desired line, having first made the usual test to obtain the idle or busy conditit'in of this line. The insertion of the calling plug into the jack of the desired li'iiecompletes a circuit from the live pole of battery 14 through the'coil of supervisory relay 41, conductor 35 contacts of the ringing key 30, sleeve contacts 36' and 22 of the'plug and jack and the coil of cut-oft relay 11 to ground. The current in this path actuates relay 11' and 41, the actuation of relay 11' connecting the line conductors 4 and 5 directly with the contacts 23 and 22 of the jacks. The actuation of relay 41' completes the circuit of supervisory signal 43 and displays that signal. The operatornow throws her ringing key 30 and sends ringing current from .her generator 57 to the tip contact 31 and 2t of the plug and jack, contacts 20 and 15 of cut-ofi' relay 11, condenser 2', annunciator 3, line conductor 5, contacts 9 and 21 of cut-oft relay l1, sleeve contacts 22 and 36 ot' the jack and plug throughthe non-inductive resistance 58 and the battery 14 to the ground pole of the generator 57. Current in this path' being alternating, passes through the condenser 2 and sounds the annunciator 3 calling the subscriber to his phone. when the called subscriber anr swers his callxla path tor acurrent is com-- -the plug and jack, contacts 21' and 9 of cutoff relay'll, line conductor 5', transmitter 6, receiver 7 switch hook 8', line conductor 4, contacts 15 and 20 of the'cut-ofl' relay 11, tip contacts 23 and 31 of the jack and plug, conductor 29, contacts 45 and 44 of relay 41, conductor 28', and the coil of supervisory relay 39 to the ground pole of battery 14'. Current in this path actuates relay 39' which severs the circuit of the supervisory signal 43; Substations land 1' are now connected for conversation and all the signals at. the central oiiice are efi'aced.

When'the subscribers again replace their receivers upon their switch hooks the circuits of relays 38 and 39' are severed andsupcrvisory signals 42 and 43 are displayed. Upon the dlsplay of these signals the operathe apparatus to return to its normal condition.

In the operation of my system when the call originates at substation 1 the subscriber in charge of that substation removes his receiver 7 from the switch hook 8 and this completes a circuit from the'live pole of battery 14through conductor 13, coil of line relay 12', contacts 10-and 9' of cut-ofl' relay 11. line conductor 5, transmitter 6', receiver 7, switch hook 8', line conductor 4 and contacts 15 and 16 of cut-oil' relay 11 to ground. The current flowing in this path energizes the line relay 12 closing its contacts. 17' and 18 and displaying the line signal 19'. p The operator observing the display of the line lamp inserts her answering plug into the line designated and thereby completes the circuits of supervisory. relays 38 and 40 and of cut-01f relay 11, these relays being-actuated to perform the same functions as relays 38, 40 and 11. The operator now obtains the desired number and finding it to be that of a subscriber connected with the ,other exchange, after testing,in-

serts her calling plug into one of the multiple jacks connected with the other exchange. A circuit is thereby completed from the live pole of battery l ythrough the coil of supervisory relay 41,--sleeve conductor 85, sleeve contacts of ringing key 30, the sleeve contacts 36" and 78 of the. plug and jack and through one of the'windings of impedance-coil 94c to ground. The.

' current in this path actuates relay 41 clo'sing'its contacts and displaying the signal 43 which indicates to the operator that the operator at the other exchange has not yet connected with the other end'of the trunk line.

Upon the insertion of the plug into the jack contacts 85 and 86 of the jack areclosed completing a circuit from the live pole of battery 14 through the coil of trunk line relay 67 contacts 66 and 65 of cut-ofi' relay-62,

trunk conductor 73, conductor 84', contacts 85 and "86 of the jack, conductor.87,.'the.

windings of polarized relay 88, the coil, of relay 83, trunk conductor 73. and the 0on tacts 71 and 7 2 of cut-oft relay 62 to ground. The current in this path energizes the trunk, line relay 67 which completes the circuit-of. the trunk line signal 70, indicating to the operator that a connection is desired over i the trunk. The operator seeing the signal 70 displayed inserts the answering plug of her cord circuit into the answering jack of the trunk and thereby completes the circuits of relays 38, {t0 and 62, actuating these relays to perform their functions as previously described. Upon the actuation of relay. 62 the direction of the current in the'trunk line is reversed, the current now flowing from the live pole of-battery 14 through the coil of relay 40, sleeve conductor 33, sleeve contacts 32 and of the plug and jack, contacts 61 and 71 of cut-off relay 62, trunk conductor 74, the coil of relay 83, the windings of polarized relay. 88, conductor 87,

contacts 86 and 85 of the jack, conductor 84:,

trunk conductor 73, contacts and 6 L of cut-off relay 62', tip contacts 63 and 25 of the jack and plug, tip conductor 26, and'the coil of supervisory relay 38 to ground. The

current in this path being in the reverse of its former direction actuates-the polarized relay 88 and closes its contacts 95' and 96,

placing a winding of the impedance coil '94:

in a bridge between the tip and sleeve contacts of the jack. This'completes a circuit from the live pole of battery 14 through supervisory relay 41, sleeve conductor 35,

sleeve contacts of the ringing key 30", sleeve 4 contacts 36' and 78 of the plug and jack, a winding of impedance coil 94:, contacts 96 and 95 of polarized relay 88, tip contacts 76 and 31 of the jack and plug, conductor '29,

contacts 45 and 44 of supervisory relay 4:1, conductor 28 and the coil of supervisory re lay 39 to ground. This actuates the relay returning to its normalcondition whenthe' answering and calling, plugs at each. exchange are removed r jacks.

While my invention isherein shownand described with respect to certain details, it is r to be understood that I do not wish vto be unduly limited thereto, the gist of the-irrvention being concerned not so much with the details of the circuit as with the results accomplished thereby, which results-could -be .,b rought about by the use of other combinations without in any way departing from thespirit or scope of'my invention.

Iclaimz. l-. In ;a telephone system, the combination 'with afpair of telephone lines terminating at diflerent switchboards, of connecting circuits at each of the switehboards, a trunk circuit extending between said swit'chboards and terminating at each end in jacks, atrunk signal at each end of the trunk line, a superom their respective The completing of the connection visory signal for each connecting circuit, and

means to display the trunk signal at either end of the trunk when a connecting circuit is connected with the other end of the trunk, and means to display the supervisory signal at the latter end of the trunk whenthe connecting circuit is-conneoted with the trunk at said end and to again eflace said signal when the connecting circuit is connected with the trunk at the opposite end, substantially asdescribed. l

2. In a telephone system, the combination with a pair of telephone lines, ofa pair of cord circuits, one adapted to be connected with each of said lines, a trunk circuit terminating at "each end in jacks and adapted to connect said cord :circuits for conversation, trunk signals, one associated with each end of the trunk, a supervisory signal for each-of Slld' cord circuits, means to display the supervisory signal at one end of the trunk and the trunk signal at the other end of the trunk when the cord circuit at the first end is connected Wlthtlle trunk,

and means to eilace both said signals when a cord circuit is connected with .the other end of the trunk, substantially as described.

3. In a telephone system, the combination with. a pair of cord circuits,of a trunk Oil? cuit terminating in jacks and adapted toconnect said cord circults for conversatlon,

signal when both cord circuits are con-' nected with the trunk, substantially as described.

4. In a tele hone system, the combination with a pair 0 cord circuits, of a trunk circuit adapted to connect said cord circuits for conversation, trunk signals at each end of said trunk adapted to be displayed when the cord circuit is connected with the opposite end of the trunk and again efiaced when.

a cord circuit is connected with each end of the trunk, a supervisory signal for each cord circuit, means todisplay one of said signals when only its associated cord circuit is connected with the trunk and to efi'ace said signal when both cord circuits are conbeing adapted to interrupt the circuit of the nected with the trunk, substantially as described.

5. In a.telephone system, the combination with a trunk line, of a relay and condenser normally in series with the trunk atone end thereof, a cord circuit adapted to be connected with the other end of the trunk, a source of alternating current, means to send alternating current over the trunk line and through said relay and condenser when the cord is connected with the trunk at the latter end, whereby said relay is actuated,'a signal displayed by the actuation of said relay, and means for disconnecting said relay andcondenser from said trunk, substantially as described.

6. In a telephone system, the. combination with a trunk circuit, of a line relay and a source of direct current normally in series therewith at the first end of the trunk, and

a line relay and condenser normally in series. therewith at the second end .of the trunk,

- adapted when actuated to interrupt the. circuit of the line .relay at that end, and a cut-off relay at the second end of the trunk witnesses.

line relay at the second end, cord circuits to connect with each end of the trunk, and

means to actuate the cut-off relays at each end when the cordsvare connected with the trunk at each end, substantially as described.

7. In a telephone system, the combination with a trunk line, of a pair of cord circuits, oneadapted to be connected with each end of the trunk, a supervisory signal for each of said cord circuits, the supervisory'signal at one Tend of said trunk being adapted to be displayed when the cord at that end is connected with the trunk, and the cord at the other end is disconnected therefrom, and adapted to be efl'aced when the cord at the latter end is connected with the trunk, substantially as described.

8. In a telephone system, the combination with a trunk circuit, of similar cord circuits adapted to be connected with the opposite ends of said trunk, a pair ofsupervisory relays associated with each of said cord circuits, a supervisory signalfor each of said cord circuits controlled by the joint action of said relays, means to complete the circuit of one of said relays when the cord is con-- nected with the trunk and no connection is established with the other end of the trunk, whereby the supervisory signal is displayed, and means to complete the circuit of the other of said supervisory relays when a connection is established with the trunk at the other end, whereby saidsu ervisory signal is again efi'aced, said trunk eing adapted to control said signals in the same manner when used in either direction, substantially as described. i I

9. In a telephone system, the combination with a trunk line, of a source of current .having its positive pole normally connected with alimb at one end of the trunk line, and a polarized relay at the other end of the trunk line adapted to receive current from said source but adapted to remain in its normal condition during the liow of current in one direction, and means to reverse the direction of current flow' from said source over the trunk line when a connection is established with the trunk at one end, whereby said polarized relay is actuated,and a signal controlled by the actuation of said polarized relay, substantially as described.

Si ed by me at Ghica 0, county of Cook, and tate of Illinois, in t e presence of two FRED ,M. DAVIS. Witnesses: a

CIHTORD O. BRADBURY,*"* I MARJORIE E. Gums. 

